Recommendation ITU-T G.8273.4/Y.1368.4 specifies minimum requirements for time and phase synchronization equipment used in synchronization networks that operates in the assisted partial timing support (APTS) and partial timing support (PTS) architectures.

Amendment 1 to Recommendation G.8273.4/Y.1368.4 provides the following updates:

Changes in clauses 2, 4, 6, 7.2, 7.3, 7.6.2, 9.1, Annex A, Annex B and Bibliography

Adds Appendix VI: PTP Noise Tolerance Testing for PTS and APTS Clocks